Two weeks ago, when Al Gore's presidential hopes appeared to be slipping with each new poll, he took a call from his boss, the president. Otherwise shut out of his deputy's campaign, Clinton urged vice-president Gore to watch a Saturday Night Live parody of his TV debates with his Republican rival. After first resisting, Gore acceded to Clinton's almost unerring political instinct. The tape revealed the public's perception of the candidate and his media-genic shortcomings that no pollster or focus group could have bettered.

Clinton touched on one of the few political realities of this campaign - that TV comedy has become one of the few clarifying elements of a political discourse obfuscated by hours of punditry, spin and anti-spin. As Americans tune out from serious political coverage and analysis, they are getting more of their election news from late-night talk. A recent survey found that 47% of people aged between 18 and 29 often gleaned information from these programmes, along with a quarter of all adults.

"So much coverage in the main stream press is dishonest and manipulative," says Columbia University journalism professor Craig Wolff. "To me, the humorists are in some ways presenting the most honest coverage."

Politics as TV comedy is hardly new and has been gaining momentum since Richard Nixon appeared on the 60s show Laugh-In. What's new is just how blurred the line between politics, news and entertainment has become. Late-night comedy talk shows such as those of Jay Leno and David Letterman have become political essentials, both as barometers of how the campaigns are playing ("If it makes it onto Leno or Letterman that really means something," said Gore press secretary Chris Lehane recently) and through appearances by the candidates themselves - a way of personalising their brand.

To former Texas governor Anne Richards, it's become almost more important for candidates to show a sense of humour than to demonstrate a grasp of the issues when debating their opponents. A good joke can be incredibly effective in getting your message out, she says, "because people repeat it". And that's invaluable for politicians because with an electorate disenchanted with politics and an election said to hinge on a small number of swing voters, humour has become one of the few ways of gaining attention.

"It's a question of the different people you need to reach," says political columnist-turned satirist Arianna Huffington. "There are people who already agree with you, and you can says things as flatly and blandly as you want, and they're with you. But then there are those who need to be convinced that the election matters."

But while Gore has appeared on Letterman and Leno, and Bush has kissed Oprah Winfrey on Oprah, been on a morning talk show with Regis Philbin, the host of Who Wants to be a Millionaire?, and had an unhappy (and un-repeated) experience on Letterman in March, none of the current crop of candidates besides Gore's democrat running mate Al Lieberman have dared venture on to The Daily Show on Comedy Central.

The programme, hosted by Jon Stewart, has emerged as America's sharpest satire. First broadcast in 1996, The Daily Show has become one of the few programmes smart enough to come close to capturing the absurdity not just of the US political process but of the media that cover the news and the pundits that interpret and re-interpret it.

In a show presented as a seemingly real newscast, Stewart and his team of correspondents spoof what increasingly feels like unreal news. As the 37-year-old Stewart himself liked to quip during coverage of the political conventions in the summer: "We're a fake news organisation covering a fake news event." But that didn't stop the game (and very funny) senator Bob Dole appearing as the programme's deskbound political pundit, or John McCain agreeing to be interviewed by Stewart faking a real interview.

In creating a comedy show that looks like a news broadcast, The Daily Show's formula is to satirise every element of the political process, from the pretensions of the candidates themselves to the over-heated pronouncements of pundits.

Some is semi-subtle (Stewart explaining that when Bush says "subliminable" instead of subliminal, he was probably thinking of "executing some criminables"). Some is not. At the Republican convention a shot of Bush sitting with his wife appeared to reveal an erection. "Welcome to the Johnson administration," quipped the commentary.

Since the primaries in January The Daily Show has been covering the election as part of its nightly look at news and events. Indecision 2000, as the political segment is called, is just one part of the proceedings but one that has established the show. Stewart, who started out as a stand-up comedian, and last year made the list of People magazine's 50 Most Beautiful, understands exactly what it's about: "The longer I'm doing this I'm coming to learn that entertainment, politics and the media are really just juggling the same balls. We're all going for ratings, so we function by the same rules. What's a political poll other than a focus group for a television show?"

Madeleine Smithberg, co-creator of The Daily Show, dates comedy's new importance to the political process from the occassion when Clinton went on the Arsenio Hall show in 1992 and played the saxophone. "That signalled a whole new ballgame," she says. "This year there's this huge emphasis on entertainment and whether the candi dates can be funny. But it's not like they have stopped doing Sunday morning television or serious talk shows. It's just that we now have this unbelievable proliferation of media venues and everyone is just hedging their bets. Maybe they'll be showing up on sitcoms or on Millionaire. Everyone is pretending they're in it for some sort of noble motive. But we're in it for the laugh. We get to pinpoint the absurdities rampant throughout the system."

There's no doubt that the constraints of US political life have played into the hands of the satirists, and that the Lewinsky affair finally stripped politics of its last vestiges of propriety. In this election - beyond Bush's aptitude for malapropisms, non-sequiturs and plain nonsense, and Gore's dull monotone - the candidates played themselves into the hands of satirists as never before by going to great lengths to say as little as possible.

On Oprah, for instance, the hostess gave each one hour to tell the electorate how much they loved their family and name their favourite food, plus a filmed report called "Remembering Your Spirit" on how the Gores and the Bushes preserve the spirit of their marriages. If getting votes means appearing with a man who smashes wooden planks on his head (as Bush did on Letterman) or singing My Way (as Lieberman did on Conan O'Brian) so be it.

"All you really do with comedy," says Jay Leno, "is clarify the news a little. Your role is to take the spin out of the story and get to the joke at its heart." CNN's chief political analyst Wolf Blitzer concedes that comedy now has an elevated role in the process. "There's no doubt all this comedy has an impact," he told the New York Times. "Elections are won and lost on public perception in that kind of popular culture."

But as the hunt to find and win over the crucial but possibly non-existent "undecided voter" peaks before the November 7 vote, US comedians know they have a golden opportunity. To Smithberg, the quest for the undecided voter is itself absurd. "It's ironic, because the undecided voter has become the most empowered voting block, and these are people who are absolutely incapable of making a decision. We've somehow given this most important decision over to the idiots who can't make a decision! We've empowered the fools."

If, by some strange fluke, Smithberg's fools are also the ones who watch The Daily Show when it beams out of New York on weekday nights at 11 pm, then late-night comedy might indeed prove to be the deciding factor in the election. But there's really no way of telling. On election night, Stewart and his gang of correspondents will be on duty pinpointing the comedy that is the marriage between political discourse and the media. "We'll be pinpointing the absurdities. We'll be doing the analysis of the analysis and then analysing that."

Presidential comedy: the contenders

Jay Leno

Lantern-jawed stand-up comic who inherited the Tonight show from Johnny Carson. Refuses to disclose political allegiance because it "taints the issue. It's like you go to a party and girls say about you 'That guy's gay.' Well, you've lost half the crowd already". Regular segment involves him quizzing ordinary Americans on the street - 6 out of 10 can't identify Al Gore.

Best campaign gag: "They executed a guy with an IQ of 63. Can you believe it? Bush turning his back on one of his own!"

David Letterman

Formerly hosted off-the-wall post-midnight show which influenced the likes of Jonathan Ross in UK; now Leno's big late-night (but not so late) rival. Both candidates have guested on his Late Show: Gore read out a Top 10 list including: "Remember America - I gave you the Internet, and I can take it away. Think about it."; Bush made a tasteless and contorted reference to Letterman's recent heart surgery. The audience booed their disapproval.

Best campaign gag:

"Al Gore spent the day at the beach with his family. And, I believe, to relax, George W Bush watched an execution."

Jon Stewart

Fronted The Jon Stewart Show from 1994-95; then took over The Daily Show in a four-year, $6m deal that also allows him to pursue his acting career. Made regular appearances on The Larry Sanders Show where he played a spoof guest host gunning for Sanders' job.

Best campaign gag:

(On the video of Bush talking about his "subliminable" RATS advertising) "Yes, he said 'subliminable'. But he was probably distracted, thinking about executing some criminables."